"The Sith Lord had grotesquely adapted the Rakatan device to draw energy directly from chained Jedi captives. He replenished his life force from the captives by draining theirs. Malak was nearly unstoppable..."
―Star Wars Databanks
Realistically, he could have beat Malak anywhere from 3-9 times (the fact it is plural means Malak at least replenished himself twice), it's unconfirmed though. I seen some who like to stick with 3, while others tend to drag all the way to 9. I personally just stick in the middle around 6, which is still ridiculously insane for Revan, since Malak is among the most powerful Sith in the mythos.